In the haulage of bulk goods such as heavy machinery, steel rods and coils, sod and non-prepackaged consumer goods, it is often desirable to ship the goods via a flat bed truck or train trailer. Conventional truck or train trailers consist of a flat rectangular trailer bed surface characterized by parallel longitudinal sides and lateral ends. It is known to cover the goods on the trailer with a tarp to protect the goods from exposure to the elements and, in the case of goods such as sod, to prevent debris and/or detritus from blowing from the trailer. In the most basic construction, the trailer is provided with a number of removable U-shaped metal bows which are used to support the flexible cover or tarp above the load while protecting it from the environment. Typically, the bows consist of a single length of bent tubular steel stock. The ends of the bows are removably secured in a complementary sized slot or hole formed along the opposing longitudinal sides of the trailer bed.
Conventionally, the trailer beds are enclosed by manually securing the tarp in place stretched over both the bows and the load on the trailer by means of shock cords and/or hold-down straps. When loading or unloading the trailer, the shock cords used to secure the flexible tarp in place stretched over the bows are manually released and the cover manually pulled aside. Once the cover has been removed, the driver or warehouseman removes the bows by pulling their ends from the slots in the trailer bed. Once removed, access to the surface of the trailer bed may be obtained along one or both of its longitudinal sides. Thereafter, the goods to be shipped are placed on the bed and the bows and cover are repositioned.
The manual positioning of the tarp typically requires that the driver or individual loading the trailer climb overtop of both the trailer bed and the load, while simultaneously positioning the tarp and re-securing it in place with the shock cords. The manual positioning of the tarp is both time consuming and inefficient. Furthermore, in physically climbing overtop of the loaded goods, there is increased risk of injury if, for example, the individual falls off the trailer and/or trips or falls on the loaded goods.
In an effort to simplify the manual loading and/or unloading of trailers, various individuals have proposed tarp covering or enclosure systems. U.S. Pat. No. 5,152,575 to DeMonte et al discloses a tarp enclosure system which incorporates a number of horizontally slidable U-shaped bows which are used to collapse or extend a cover over the top of a truck trailer bed in an accordion-like manner. The Wahpeton Canvass Company of North Dakota has sold in conjunction with its trade mark SHURCO™ various enclosure systems which are adapted to be rolled or unrolled horizontally over the open top of dump truck and grain trailer bins.
Heretofore, however, the marketplace has achieved little or no success in providing vertically retractable tarp systems which are adapted to permit lateral access to a flat truck or railcar trailers which have bows which are either permanently secured to the trailer bed, or which are removable for loading and unloading goods thereon.